Recovery of aluminum chloride catalyst



1957 T. R. BELL ET AL RECOVERY OF ALUMINUM CHLORIDE CATALYST Filed April 29, 1954 m w u3 wwm m mm m zo .6 mh mmo. mm w. -59 2.8 m3 5:; 3 o mm .25 :2; F a 582: N 12?. W E 2 69m M5255 m2 0? V m; JOI ON 554% \N m? mizwzmfiom 3.2 58.6 It; 0 m3 S52E35 .533 mwmmnmom w 25 to ZOE-0300mm W49 IQ mo. mwmoomm F .d 6 w 2 6 2 6 2 "5 mi: mm

' THOMAS ROBERT BELL AND BY PAUL GORDON HAINES A G. Dcvndmum- United States Patent RECOVERY OF ALUMINUM CHLORIDE CATALYST Thomas Robert Bell, Straiford, and Paul Gordon Haines, Lafayette Hill, Pa., assignors to Pennsalt Chemicals Corporation, a corporation of Pennsylvania Application April 29, 1954, Serial No. 426,492

7 Claims. (Cl. 260-449) This invention relates to a method for the'production of chlorinated polyphenyls from hexachlorocyclohexane, or benzene hexachloride, a major advantage of the process being that a large portion of the anhydrous aluminum chloride catalyst is recovered in anhydrous and readily reusable form.

In the manufacture of the gamma isomer of benzene hexachloride, which is useful as an insecticide, a large quantityof other isomers of benzene hexachloride is obtained as a by-product, and various procedures have been utilized in an attempt to convert the alpha and beta isomers into useful chemical compositions since they possess no insecticidal activity. I

In U. S. Patent 2,569,441 there is disclosed a process in which benzene hexachloride may be converted catalytically to trichlorobenzene, the process comprising the treatment of benzene hexachloride with 0.5 to percent of its weight of anhydrous aluminum chloride, at a temperature between 125 and 225 C.

Into-pending application Serial No. 422,992 filed it is disclosed that chlorinated polyphenyls may be produced from benzene hexachloride by reaction of the benzene hexac'hloride with a reactive aromatic compound in the presence of an aluminum chloride catalyst. Among the reactive-aromatic compounds which may be employed are the incompletely halogenated benzene derivatives, e. g., mono-, di-, triand tetrachloroand bromo-benzenes, and trichlorofluorobenzene, diphenyl, naphthalene, and the isomeric xylenes. The preferred-reactive aromatic compounds are di -and trichlorobenzenes. Exemplary of nonreactive substituted aromatic compounds is nitrobenzene, the use of which fails to produce any chlorinated polyphenyls in the method of the invention.

The process of the present invention constitutes an improvement over the process disclosed in the above-identifijedlco-pendingapplication in that, in the process of the present'invention, the efiiuent reactor gases, and the materials entrained therein, are passed into a scrubbing tower containing a circulating organic compound, which is preferably aromatic innature. The efiiuent reactor gases consist primarily of hydrogen chloride containing entrained particles of aluminum chloride catalyst and reactive aromaticcompound. These materials are carried down the scrubber tower by the scrubber liquid to a decanter from which hydrogen chloride gas is released and passed into a conventional absorbing tower. The scrubber liquid, and reactiveraromatic compound admixed therewith, is decanted for reuse in the process and a slurry of aluminum chloride catalyst in the scrubber liquid is also sep-- arated from the decanter for recycle to the catalyst feed hopper.

The reactive aromatic compound is preferably identical with the compound employed for the scrubber liquid: Hence,'when trichloroben'zene is employed as the reactive aromatic compound and also as the scrubber liquid, the trichlorobenzene may be passed from the decanter directly into the reactor for further use in the process and the slurry of aluminum'chloride and trichlorobenzene may be recycled to the reaction zone, without separation of the catalyst from the scrubber liquid.

H 2,812,370 Patented Nov. 5, 1957 The concentration of anhydrous aluminum chloride catalyst may be 2 to 30 percent by weight of the original benzene hexachloride charged and is preferably 10 to 25 percent of the benzene hexachloride initially present. The reaction temperature may be within the range of to 225 C., with the reflux temperature of the reaction mixture being within the range of 220 to 225 C. The reaction time may be in the range of 2 to 30 hours.

The reaction mixture may contain 0.25 to 2 parts by weight of reactive aromatic compound for each part by weight of benzene hexachloride. Larger quantities of aromatic compound require more aluminum chloride catalyst to obtain complete reaction of the benzene hexachloride, whereas the use of smaller quantities results in a lower yield of chlorinated polyphenyls.

Referring to the accompanying drawing, a' flow diagram of the process of the invention is shown in which the reactor 2 is equipped with a charging line 4 for benzene hexachloride and reactive aromatic compound, which in the embodiment shown is trichlorobenzene, a .line 6 for admitting dry gas and a line 8 for charging aluminum chloride. The benzene hexachloride and trichlorobenzene are reacted in the reactor 2 in the presence of the aluminum chloride catalyst while heating the reaction mixture at reflux temperature so that the major portion of the hydrogen chloride gas evolved from the reaction mixture is evolved in approximately 2 hours. connecting the reactor 2 and the scrubber 12 is heated in order to prevent blocking thereof by sublimation.

.Hydrogen chloride gas begins to be evolved from the reaction mixture at a temperature of about 100 C. and

continues to be evolved until the reaction is complete.- Heating of the reaction mixture at reflux temperature is continued until hydrogen chloride evolution ceases and then a dry, inert gas, such as air or nitrogen, is passed into the reactor 2 through the line 6.for aperiod of approximately 1 hour. This dry air entrains the major portion of the aluminum chloride catalyst and carries it through the line 10 into the, scrubber 12, It. isthen car:

ried into the decanter 14 by the circulating trichlorobenzene in the scrubbing tower, this. material being circulated by the pump .16. The hydrogen chloride gas released from the decanter 14 passes to any conventional absorbing tower, not shown, by way of the line 18[ The scrubber liquid in the decanter 14 settles into two layers, the lighter of which is primarily trichlorobenzene and the heavier of which is a slurry of anhydrous aluminum chloride catalyst in trichlorobenzene. The trichlorobenzene layer may be decanted and passed into the reactor 2 through the linev 20 for further reactionwith benzene hexachloride or may be passed into the product wash tank through the line 22. The slurry of aluminum chloride catalyst in trichlorobenzene is passed by the pump 16 through the line 24 into the aluminum chloride feed hopper 26, which has a line 28 connected thereto for the-addition of make-up aluminum chloride catalyst.

The reaction mixture is passed through the line,30 into the product wash tank 32, having a line 34 connected thereto for the addition of sodium hydroxide solution. The reaction mixture is washed in the product wash tank with sufficient sodium hydroxide, at a temperature of and then with dilute sodium hydroxide solution to re-'' moveithe acid. If the reaction mixture is too viscous to wash, it is diluted with trichlorobenzene.

The line 10 The Washed product, without drying, is then passed through the line 35 into the still 36, where it is distilled first at a pressure of 20 to 30 mm. of mercury absolute to remove the water and trichlorobenzene fractions, indisolute, and a product, Cut 2, which was an amber colored resin boiling at a temperature of 215 to 280 C. at a pressure of 0.3 mm. Hg absolute. The remainder of the material was a brittle black still pot residue.

cated at 38 and 40 respectively. Unslaked lime,(calcium 5 Two successive runs were made in each of which 2000 oxide) is then added to the still pot and distillation is grams of mixed alpha and beta isomers of benzene hexacolltilllled {0 Obtain a Product, Cut and a P chloride were charged to the reactor, together with tri- Cut 2, 44. The still pot residue 46 i brittlfi black chlorobenzene from the decanter and a small portion of solidi make-up trichlorobenzene. Aluminum chloride catalyst The recovery 0f aluminum ch'lvride Catalyst from t 10 slurry from the decanter was employed together with a scrubber liquids in accordance with the process of the m- Small quantity of makemp Catalyst venue y be between 72 and Percent by welght In run No. 2, 1585 grams of aluminum chloride slurry of the alumlnum Chloride catfllystioflglflally charged, and were charged to the reactor, which consisted of approxiaverages about 83 percent. mately 444 grams of anhydrous aluminum chloride and The invention will be further illustrated by reference 1141 grams of trichlorobenzenfl To this mixture wem to the following speclfi p added 52 grams of make-up trichlorobenzene and 60 EXAMPL l grams of make-up anhydrous aluminum chloride catalyst. 2000 grams of i mixed alpha and is lsoners of In run No. 3, 1754 grams of aluminum chloride slurry benzene hfixachlonde 1200 grams 9 mc enzene and trichlorobenzenc were charged to the reactor, of and 500 grams of anhydrous. aluminum chloride were i wh1ch approximately 458 grams were aluminum chloride charged mm a 5-hter, 3-neclled flask equipped with a thermowell and a Glascol heater. The reaction mixture and 1296 grams were trlehlerobenzene- To this mixture was gradually heated; evolution of hydrogen chloride gas were added 50 grams of -P tl'lehlolobenzene and therefrom began when a temperature of 100 C. was 60 grams of P anhydrous alumlmlm Chloflde caia' reached and continued while the reaction mixture was lystheated to reflux temperature. The reaction mixture was The results of these runs are as follows:

Table 1 Reactants Conditions Products Remarks Run No. a,B-BHO A1013 charged TCB charged Tcmp., Time, H01, Cut 1 Cut; 2 Residue charged, g. 0. hrs. g.

1 2,000 500 g 1,200g 100230 3 945 Products of three nms combined as z ri gilgz found 2 2,000 1,585 g. slurry: 418 g. from scruh- 100-230 3 930 Products cf three runs combined 42.1 g. AlClrfound lccs it tl gg; be; +52 g. makein product. I 3 "ta-tastes: 3 942 enet. TOB=1,296 g. up. 1;. AlCh found in scrubber.

refluxed for a period of about 2 hours and the hydrogen The chlorinated polyphenyls produced by the process of chloride gas evolved from the reaction mixture, together the invention find w1de industrial application, e. g., as with the entrained material therein, was passed through dielectrics, hydraulic IHGdlUl'l'hS lubricants impregnatmg a wide diameter glass tube to a glass scrubbing tower materials, plasticizers and additives for use in paints, var containing anhydrous trichlorobenzene circulated by a nlshes and waxes. Monel metal pump through a Monel metal circulating It W111 be obvious to those sk 1lled 1n the art that many line. The hydrogen chloride gas then passed into a demodifications may be made within the scope of the present canter and through a simple trap to remove any liquid invention without departing from the spirit thereof, and spray, after which it was passed into an absorbing tower the invention includes all u h m d fi ati containing circulating sodium hydroxide, the tower being 55 We claim: I mounted on a balance for continuous weighing. 1. In the aluminum chloride catalyzed process for the At the end of the two-hour heating period, the evoluproduction of chlorinated polyphenyls by reaction of hention of hydrogen chloride gas substantially ceased, and a zene hexachloride with a reactive aromati compound, the rapid flow of y air was Passed through the miXtllfe improvement for recovering the aluminum chloride catafor 3 Period 0f about one 110111 While the reaction 1 lyst comprising maintaining the reaction product mixture 1 W Was maintained at a temperature near its near its boiling point while entraining the said catalyst in. Point Thfi flow of dry air served to separate the l an inert gas leaving the reactor, directing the gas with ity of the aluminum chloride catalyst from the reaction contained catalyst into a Scrubbing tower, Scrubbing mixture and the catalyst i unified by entrainment mm said gas with an aromatic liquid, discharging the said the trichlorobenzerie circulanng m the scrubber 35 liquid containing the catalyst from the scrubbing tower The reaction. mlxture. was then cooled Washed ,wlth and returning the catalyst to the reactor for reuse. sodium hydroxide solutlon at a temperature of 100 hC 2 The procgss according to claim 1 in which the cam, to remove. alummune salts and The was 6 lyst is separated from the major portion of the scrubbing product, without drying, was then distilled at a pressure H b 9 6 the catal st is rammed to the reactor of 20 to 30 mm. of mercury absolute to remove the water e y 1 2 h and trichlorobenzene therefrom. Unslaked lime (cal- The PQ accordlng t0 0 111 In wrlc d e reg:- cium oxide) was then added to the still pot in an amount five awmafic g p and the scrubber q are e 3 ercent of the wei t of the still pot contents, Same compoun I I z d dieiillat ion was continued ih obtain a product, Cut 1, 4. The process according to claim 1 in which the cat;- as a nearly colorless viscous liquid boiling at a temperalyst 1s separated from tne scrubbing liquid be ore t e ture of 150 to 215 C. at a pressure of 0.2 mm. Hg abcatalyst is returned to the reactor.

5. A process according to claim 1 in which the reactive aromatic compound has the formula 7. A process according to claim 1 in which the reactive aromatic compound has the formula in which n is an integer from 1 to 4.

References Cited in the file of this patent UNITED STATES PATENTS Jackson et a1 Sept. 29, 1936 Alquist et al Oct. 2, 1951 

1. IN THE ALUMINUM CHLORIDE CATALYZED PROCESS FOR THE PRODUCTION OF CHLORINATED POLYPHENYLS BY REACTION OF BENZENE HEXACHLORIDE WITH A REACTIVE AROMATIC COMPOUND, THE IMPROVEMENT FOR RECOVERING THE ALUMINUM CHLORIDE CATALYST COMPRISING MAINTAINING THE REACTION PRODUCT MIXTUREE NEAR ITS BOILING POINT WHILE ENTRAINING THE SAID CATALYST IN AN INERT GAS LEAVING THE REACTOR, DIRECTING THE GAS WITH CONTAINED CATALYST INTO A SCRUBBING TOWER, SCRUBBING THEE SAID GAS WITH AN AROMATIC LIQUID, DISCHARGING THE SAID LIQUID CONTAINING THE CATALYST FROM THE SCRUBBING TOWER AND RETURNING THE CATALYST TO THE REACTOR FOR REUSE. 